1. Technical Field
This invention primarily relates to the field of two interactive entertainment systems typically provided over cable facilities to a user and, more particularly, to terminal method and apparatus enabling a programmed background audio or video signal to be displayed as a background at an associated television receiver.
2. Description of the Relevant Art
Two way interactive cable television systems are known for transmitting entertainment, information and data signals over a cable facility toward a plurality of users. Data may be transmitted and addressed to a particular subscriber over a separate data channel, out of band, or a so-called "in-band" data channel within the video signal, for example, in the vertical blanking interval. In a downstream direction, addressed control data may represent services authorized to a particular terminal or control commands to that terminal. In an upstream direction from a terminal to the service provide or system manager location, control data may represent selections made by a user in response to a polling request or at the time of user selection.
Terminals are often manufactured with stored unique identification numbers which may be unknown to a user for security purposes. Nevertheless, the unique identification number is necessary for the system manager to address a terminal in the system. When video and audio services are requested from the terminal, the address is used to specifically indicate destinations for services requested so that information associated with delivery of a requested service may be delivered to the requesting terminal.
In the instance of teletext services, screens of at least textual characters are delivered to terminals and are displayed on an associated television receiver. According to Campbell et al., U.S. Pat. No. 4,536,791, an addressable cable television terminal comprises a text/graphics generator. Data signals including control and text signals are inserted on the vertical interval of television signals transmitted to the terminal. Moreover, full-channel teletext data in video line format is transmitted to the terminal on dedicated text channels. Data retrieved from the transmitted television signal may be overlaid on the image created by the video signal. For example, a channel number retrieved from the vertical interval can appear in the foreground and a tuned-to program appears in the backgrounds of a display.
It is also known in a television receiver to selectively tune to a radio broadcast of an audio signal for accompanying a video program. In this manner, stereo audio or audio in a foreign language may accompany a television program whose audio portion is neither stereo nor in the selected language.
A requirement, however, exists in the art for a selectable overlay of text upon a video program or an audio program or both to accompany a text screen. For example, in the provision of premium television program services, textual instructions would selectively and programmably be displayed in the foreground and a preview of a premium program appear in the background with or without accompanying audio. In the presentation of teletext screens offering room service in a hotel room and advertising dinner selections, dinner music may be tuned and played in the background from a dinner musice audio channel and accompany the teletext screens for room service as they are displayed.